In view of the wide variety of products that are sold for being dispensed from containers, particularly containers with round necks which define the dispensing portal, numerous constructions have evolved for container stoppers or closure means for the portals, including for example screw caps, stoppers, corks and crown caps, to name a few. Generally, products such as vinegar, vegetable oils, laboratory liquids, detergents, honey, condiments, spices, alcoholic beverages, and the like, have similar needs regarding the type and construction of the closure means used for containers for these products. However, wine sold in bottles represents the most demanding product in terms of bottle closure technology. In an attempt to best meet these demands, most wine bottle closures or stoppers have been produced from a natural material known as “cork.”
While natural cork still remains a dominant material for wine closures, synthetic wine closures have become increasingly popular over the last years, largely due to the shortage in high quality natural cork material and the awareness of wine spoilage as a result of “cork taint,” a phenomenon that is associated with natural cork materials. In addition, synthetic closures have the advantage that by means of closure technology, their material content and physical characteristics can be designed, controlled and fine-tuned to satisfy the varying demands that the wide range of different wine types produced throughout the world impose on closures.
One of the principal difficulties to which any bottle closure is subjected in the wine industry is the manner in which the closure is inserted into the bottle. Typically, the closure is placed in a jaw clamping member positioned above the bottle portal. The clamping member incorporates a plurality of separate and independent jaw members which peripherally surround the closure member and are movable relative to each other to compress the closure member to a diameter substantially less than its original diameter. Once the closure member has been fully compressed, a plunger moves the closure means from the jaws directly into the neck of the bottle, where the closure member is capable of expanding into engagement with the interior diameter of the bottle neck and portal, thereby sealing the bottle and the contents thereof.
In view of the fact that the jaw members are generally independent of each other and separately movable in order to enable the closure member to be compressed to the substantially reduced diameter, each jaw member comprises a sharp edge which is brought into direct engagement with the closure member when the closure member is fully compressed. Score lines are frequently formed on the outer surface of the closure member, which prevents a complete, leak-free seal from being created when the closure member expands into engagement with the bottle neck. This can occur, for example, if the jaw members of the bottling equipment are imperfectly adjusted or worn. Leakage of the product, particularly of liquid product, from the container can thus occur.
Thus, it is generally desirable that any synthetic bottle closure be able to withstand this conventional bottling and sealing method. Furthermore, many cork sealing members also incur damage during the bottling process, resulting in leakage or tainted wine.
Another issue in the wine industry is the capability of the wine stopper to withstand a pressure build up that can occur during the storage of the wine product after it has been bottled and sealed. Due to natural expansion of the wine during hotter months, pressure builds up, which can result in the bottle stopper being displaced from the bottle. As a result, it is generally desirable that the bottle stopper employed for wine products be capable of secure, intimate, frictional engagement with the bottle neck in order to resist any such pressure build up.
A further issue in the wine industry is the general desirability that secure, sealed engagement of the stopper with the neck of the bottle be achieved quickly, if not virtually immediately after the stopper is inserted into the neck of the bottle. During normal wine processing, the stopper is compressed, as detailed above, and inserted into the neck of the bottle to enable the stopper to expand in place and seal the bottle. However, such expansion desirably occurs immediately upon insertion into the bottle since many processors tip the bottle onto its side or neck down after the stopper is inserted into the bottle neck, allowing the bottle to remain stored in this position for extended periods of time. If the stopper is unable to rapidly expand into secure, intimate, frictional contact and engagement with the walls of the neck of the bottle, wine leakage can occur.
It is further desirable that the closure be removable from the bottle using a reasonable extraction force. Although actual extraction forces extend over a wide range, the generally accepted, conventional extraction force is typically below 100 pounds (445 Newtons).
In achieving a commercially viable stopper or closure, a careful balance must be made between secure sealing and providing a reasonable extraction force for removal of the closure from the bottle. Since the these two characteristics are believed to be in direct opposition to each other, a careful balance must be achieved so that the stopper or closure is capable of securely sealing the product, in particular the wine in the bottle, preventing or at least reducing both leakage and gas transmission, while also being removable from the bottle without requiring an excessive extraction force.
Furthermore, it is generally desirable that the closure has a low oxygen permeability. Too much oxygen can cause the premature spoilage of wine. In fact, oxidation may occur over a period of time to render the beverage undrinkable. Thus, it is desirable to effectively prevent or reduce oxygen from entering the bottle in order to extend and preserve the freshness and shelf life of the product. Any commercially viable wine stopper or closure should therefore generally have a low oxygen transfer rate (OTR).
In addition to the above, it is also desirable, for economic and environmental reasons, to reduce the total amount of material in a synthetic closure, particularly the amount of synthetic material. Since the size of the closure is determined by the size of the bottle neck, reducing the amount of material can principally be achieved by reducing the density of the closure, in particular of the core member, which is generally in the form of a foamed material comprising air- or gas-filled cells. However, reducing the density of the core member generally increases the deformability of the core member and thus of the synthetic closure, which in turn results in a worsened sealing capability and thus in increased leakage. In order to avoid this, a thicker and/or denser outer layer or skin is conceivable, as is the incorporation of a stiffer and/or denser central element within the core member. However, either of these approaches increases the total amount of material, thereby diminishing or even eliminating any advantages achieved by reducing the core density. It is also possible to reduce the amount of synthetic material by using filler material. Closures are known which incorporate natural or synthetic fibres into a synthetic matrix. For example, U.S. Pat. No. 6,085,923 describes a stopper made of a synthetic elastomer body containing a fibrous plug, or one or more fibre portions oriented longitudinally, in the elastomer body. The fibres are stated therein to reinforce the stopper, whereby the stopper body, and thus properties such as oxygen transfer and permeability, are not homogeneous. It would be advantageous to be able to control the properties of a closure incorporating filler material, in particular natural filler material, in the same way as a synthetic closure. It would be particularly advantageous to be able to achieve homogeneous properties within such a closure. It would also be advantageous to be able to ensure that the desirable properties for such a closure, for example making it suitable as a closure for a wine bottle, as described herein, are achievable in industrial scale production without significant deviation for individual closures.
In addition to the above, it is often desirable for synthetic closures to resemble natural cork closures as closely as possible in appearance. Both the longitudinal surface and the flat ends of cylindrical cork closures generally have an irregular appearance, for example showing naturally occurring irregularities in color, structure and profile. Methods have been developed for providing synthetic closures with a physical appearance similar to natural cork, for example by blending colors to produce a streaking effect in the outer portion of the closure, along the cylindrical axis, or to provide the flat terminating ends of a synthetic closure with a physical appearance similar to natural cork.
The cork industry generates large quantities of cork powders resulting from the final stages of cork processing or from existing cork products. Such cork powders are generally considered to be waste products and are burned to feed boilers in industrial processes. It would be advantageous to transform cork powders into a high value composite product. It is known to incorporate cork powders and cork granulates into composites with polymers. The incorporation of cork powder into a synthetic matrix can, however, be detrimental to the processing and performance properties thereof. Composites comprising large amounts of cork powder, for example more than about 50 wt. % of cork powder, based on the total weight of the composite, tend to have properties such as hardness, density and permeability which make them unsuitable as closures for wine bottles. In addition, crosslinkers are often required in order to improve properties. However, these crosslinkers can raise issues of food safety when used in products which come into contact with foodstuffs. Composites comprising cork granules, on the other hand, generally have the disadvantage that the cork granules distributed within the matrix contribute to or even dominate the mechanical and permeability properties of the composite, making them non-uniform throughout the composite. In order to be usable as closures for wine bottles, uniform properties throughout the closure are desirable. Furthermore, it is more difficult to remove haloanisoles, in particular trichloroanisole (TCA) and other anisoles that can cause organoleptic problems, such as tribromoanisole (TBA), tetrachloroanisole (TeCA) and pentachloroanisole (PCA), from cork granules than from cork powder, so that closures including cork granules risk the problem of so-called cork taint. Closures incorporating cork material in a synthetic matrix have been previously described. For example, FR 2 799 183 describes synthetic closures consisting of a mixture of cork granulate and cork powder in a polyurethane matrix. The mixture of cork granulate and powder is said to be necessary for the homogeneity of the closure. However, the properties of such closures are generally not homogeneous throughout because of the presence of different “zones” comprising either cork or polyurethane. Furthermore, such closures can crumble and even fall apart because of weaknesses in the matrix arising from the incorporation of larger cork granules. In addition, the preparation method for closures incorporating cork products in a polyurethane matrix generally involves combining the cork products with polyurethane monomers, oligomers, or prepolymers, and polymerizing in situ. However, residual monomers and low molecular weight compounds such as dimers, trimers, and other oligomers, remain in the matrix and/or in the cork materials. These residual monomers and low molecular weight compounds may not be compatible with food safety considerations, since they can migrate into food products which are in contact with the closure. It would be advantageous for a closure to overcome these problems as far as possible.
It is, furthermore, often desirable to provide decorative indicia such as letters and ornaments on the surface of wine stoppers (e.g. the crest or emblem of a winery). Natural corks are generally marked by a method commonly referred to as “fire branding,” i.e., by the application of a hot branding tool. Alternatively, natural corks may also be branded by application of colors or dyes. Due to food safety concerns, marking of natural corks with colors or dyes is generally only effected on the curved cylindrical surface of the cork that is not in direct contact with the wine. On the other hand, marking on the flat terminating surfaces of natural corks is generally effected by means of fire branding only since this method does not impose any food safety concerns.
It is also known to brand synthetic closures. Synthetic closures are commonly branded by means of inkjet or offset printing using special dyes or colors approved for indirect food contact. Since such colors and dyes are normally not approved for direct food contact, marking of synthetic closures with colors or dyes is generally only effected on the curved cylindrical surface of the cork that is not in direct contact with the wine. Such marking can be on the outermost surface, or on an inner surface which is subsequently covered with an outer, preferably substantially transparent, layer. Marking on the flat terminating surfaces of synthetic closures is generally only known for injection molded closures, where marking is effected during the molding process of the closure by providing raised portions on the flat terminating surfaces.
Methods are available for marking the flat terminating surface of synthetic closures that have been manufactured by means of extrusion, in particular by co-extrusion. Laser marking may, in theory, be a feasible method since it allows the avoidance of direct food contact. This method is, however, inherently slow and expensive since it requires the use of special laser dye additives. Also, there have been concerns that laser marking of the flat terminating surfaces of synthetic closures may adversely change the foam structure of the core element, which may, in consequence, adversely affect the sensitive gas permeation properties of such closures.
A further method involves the application of a decorative layer, in particular of a decorative plastic layer, by means of heat and/or pressure transfer. This method allows for permanent branding of synthetic closures without giving rise to concerns relating to food safety and without negatively impacting the gas permeation and/or mechanical properties of synthetic closures, in particular of co-extruded synthetic closures.
Therefore, there exists a need for a synthetic closure or stopper which particularly comprises at least one of the characteristic features described above, said synthetic closure or stopper having a physical appearance and/or tactile characteristics similar in at least one aspect to a natural cork closure, particularly with only minimal impairment, particularly with no impairment or even with improvement of the other properties of the closure such as, inter alia, OTR, leakage, ease of insertion and removal, compressibility and compression recovery, compatibility with food products.
Other and more specific needs will in part be apparent and will in part appear hereinafter.